This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-364814, filed Nov. 29, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a cooling unit designed to cool heat generating components such as a CPU (Central Processing Unit) and to an electronic apparatus incorporating the cooling unit. In particular, the invention relates to a structure that enhances the efficiency of cooling heat generating components.
2. Description of the Related Art
CPUs for use in electronic apparatuses such as portable computers generate heat in an increasing amount, as their operating speed increases and the functions they perform increase in number. The electronic apparatus therefore incorporates a cooling unit for cooling the CPU. The cooling unit is provided in the housing of the electronic apparatus. The cooling unit comprises a heat-receiving section, a heat sink, and a cooling fan. The heat-receiving section receives the heat from the CPU. The heat sink is thermally connected to the heat-receiving section. The cooling fan applies cooling air to the heat sink.
The cooling fan comprises a flat fan case and an impeller provided in the fan case. The fan case has a plurality of air inlet ports and an air outlet port. The impeller is designed to draw air through the air inlet ports and drive the air, as cooling air, through the air outlet port. The cooling air forced out via the air outlet port is applied to the heat sink. The heat transmitted from the CPU to the heat sink is thereby released from the heat sink, owing to the heat exchange between the heat sink and the cooling air. The heat radiates from the electronic apparatus as the cooling air flows out of the housing of the electronic apparatus.
The CPU is mounted on a printed wiring board of the electronic apparatus. The printed wiring board is provided in the housing of the apparatus, extending along the bottom wall of the housing. The cooling unit is mounted on the printed wiring board, too, with the heat-receiving section, heat sink and cooling fan arranged side by side on the printed wiring board. The impeller of the cooling fan lies horizontally on the printed wiring board, with its shaft extending in the direction of thickness of the housing of the electronic apparatus. The fan case holding the impeller is thicker than the heat-receiving section and the heat sink. Hence, the thickness of the fan case determines the maximum thickness of the cooling unit.
The printed wiring board and the cooling unit overlap, one above the other, in the direction of thickness of the housing of the electronic apparatus. It follows that the space in the housing must have a height equal to or greater than the sum of the thickness of the wiring board and the thickness of the fan case.
In recent years, however, it is demanded that the electronic apparatus of this type should have as thin and compact a housing as possible. The space within the housing, for accommodating various components, is inevitably limited. Consequently, the fan case of the cooling fan needs to be as thin as possible. As known in the art, the larger the impeller in its axial direction, the greater its air-applying ability of the cooling fan. If the fan case is thin, the impeller cannot be large in its axial direction, reducing the air-applying ability of the cooling fan. Ultimately, the cooling unit cannot cool the heat generating component with high efficiency.
An embodiment of the present invention is to provide a cooling unit which has a large cooling fan without increasing the size of the fan case and which can therefore cool heat generating components with high efficiency.
Another embodiment of the invention is to provide an electronic apparatus that has a cooling unit whose heat-receiving section can be large enough to cool the heat generating component efficiently, without increasing the size of the housing of the electronic apparatus.
To attain these embodiments, a cooling unit according to an aspect of the invention comprises: a heat-receiving section which receives heat from a heat generating component and which opposes a printed wiring board across the heat generating component; a heat sink thermally connected to the heat-receiving section and configured to release heat from the heat generating component; and a cooling fan which applies cooling air to the heat sink. The cooling fan has a fan case and an impeller provided in the fan case. The fan case is arranged side by side with the heat-receiving section along the printed wiring board. The fan case protrudes from that side of the printed wiring board which faces away from the heat-receiving section.
In the cooling unit thus constructed, the fan case can have a sufficient thickness and can therefore accommodate a large impeller. This increases the air-applying ability of the cooling fan. The cooling fan can apply cooling air to the heat sink at a sufficient flow rate. Hence, the cooling unit can cool the heat generating component with high efficiency.
Additional embodiments and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The embodiments and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.